| Objective: To evaluate the effects of tea polyphenols on Lipid metabolism and a variety of elements in rats under three dietary forms and to explore the underlying mechanisms of its effect on zinc homeostasis on food restriction rats.Method: Rats were fed normal chow diet(C), food restriction diet( 70% food intake of control group)(L) or high-sugar and high-fat diet(H) supplemented with tea polyphenols each for 18 weeks(C+G, L+G, H+G). Tea polyphenols were intaked by oral administration by 200 mg / kg body weight dose. Daily food intake and body weight were recorded; A week before the experiment, 24 h urine of rats were collected by metabolic cages. Rats were sacrificed after 18 weeks, fasting blood glucose, blood lipids, blood cholesterol, HDL-C, LDL-C, serum ALT levels were measured and liver HE staining was done. 14 elements in whole blood, 4 in urine and 6 in femur were detected by ICP-MS, and the activity of GPX enzyme in whole blood were measured.The interaction of tea polyphenols with zinc chloride in an aqueous solution were measured by UV-visible and fluorescence spectrometry. Levels of the expression of zinc related transporter proteins in liver of L and L+G group rats were measured by Real time-PCR assay.Results: 1. Effects of tea polyphenols(G) on the lipid metabolism and elements in Rats under three dietary forms:1)Body weight of L group rats were significantly lower than that in rats on C group at the end of 1th week(P < 0.05). Rats of H group increased body weight gain significantly in comparison to C group at the end of 5th week(P < 0.05); Body weight of H+G group rats was significantly lower than that in rats of H group at the end of 4th week(P < 0.05). Food intake in rats of L and H group was significantly lower than thatin rats of C group(P < 0.05). No body weight and food intake difference between C+G and L+G group rats with their corresponding control groups(C, L) were observed.Liver and testis coefficient of L group was greater than C group(P < 0.05), heart and kidney coefficient and the ratio of visceral tissue over total body weight have no difference compared with C group. The ratio of visceral fat over total body weight of H group was greater than C group(P < 0.05), but no difference in the coefficient of other organs were observed. No Liver, heart, kidney, testis coefficient and the ratio of visceral tissue over total body weight difference between C+G and L+G group rats with their corresponding control groups(C, L) were observed. Heart coefficient of H+G group rats was significantly higher than that in rats of H group, but no difference of other organ coefficient were observed.2) Total cholesterol(TC) level of rats on L group was significantly lower than that of rats on C group(P < 0.05), fasting blood glucose level was higher than that of rats on C group(P < 0.05), but no difference were observed on LDL-C,TG and HDL-C level. Fasting blood glucose, total cholesterol(TC) and LDL-C level of rats on H group were significantly higher than that of rats on C group(P < 0.05), HDL-C level was significantly lower than that of rats on C group(P < 0.05), but no difference was observed on TG level. LDL-C level of rats on C+G group was significantly lower than that of rats on C group(P < 0.05), but no difference were observed on fasting blood glucose, TC, TG and HDL-C level. LDL-C level of rats on L+G group was significantly higher than that of rats of C group(P < 0.05), TC level was significantly lower than that of rats of L group(P<0.05), but no difference were observed on fasting blood glucose, TG and HDL-C level. LDL-C level of rats on H+G group was significantly lower than H group(P < 0.05), HDL-C level was significantly higher than that of rats on H group(P < 0.05), but no difference were observed on fasting blood glucose and TC level.3) No difference between ALT activity of H group and L group with that in rats of C group was observed; but a lot of fat vacuoles were observed in the liver of Hgroup. There was no difference between C+G, L+G and H+G with their corresponding control groups(C, L, H) in serum ALT activity of rats; but there were little fat vacuoles in the liver of H+G than H group.4) No difference of 14 elements in whole blood between the L group and C group rats were observed, Ca and Zn content in whole blood of H group rats were less than C group(P < 0.05). There were no difference in Zn, As, Se, Cd, Tl, Pb content in femur between L group and H group rats. Se excretion in 24 h urine of H group rats was significantly lower than C group(P < 0.05). No difference between Ca, Zn excretion in 24 h urine of H group and L group with that in rats of C group were observed. No difference of 14 elements in whole blood between the C+G group and C group rats were observed; many elements content in whole blood of L+G group rats is difference with L group(P < 0.05); Se content in whole blood of H+G group rats is higher than H group(P < 0.05), GPX activity was higher than H group, too. Ca, Zn content in whole blood of H group rats is less than C group(P < 0.05); There was no difference in 24 h urinary excretion of Ca, Zn, Se, Tl content between C+G group and C group rats. Tl 24 h urinary excretion of H+G rats was significantly lower than that in rats on H group(P < 0.05). There was no difference in Zn, As, Se, Cd, Tl, Pb content in femur between C+G group and C group rats. Pb content in femur of L+G group rats is lower than L group(P < 0.05). Pb, Tl content in femur of H+G group rats is higher than H group(P < 0.05).2. The mechanism of tea polyphenols on zinc homeostasis of food restriction rats:Changes of the absorption peak of polyphenol in the UV-visible light was observed after Zinc chloride was added; Tea polyphenls bind zinc cations in solution with higher affinity than the zinc-specific chelator Zinquin. The expression of MT1 m RNA in liver of L+G group rats was higher than L group(P <0.05); No significant difference between L and L+G group in the expression of SOD1,Zn T1 and ZIP m RNA was observed.Conclusion:1. Long-term high-fat diet causes weight gain, abnormal serum lipid metabolism,and whole blood Ca, Zn content decrease in rats.2. Tea polyphenols can reduce the body weight gain induced by high fat diet which is independent on the influence of food intake, but do not affect the body weight of normal diet and food restriction rats.3. Tea polyphenols can improve serum lipid abnormalities and liver steatosis induced by high fat diet, but can not improve Ca and Zn content which were decreased by high fat diet.3. Food restriction do not cause a change of 14 elements in the whole blood of rats.4. Tea polyphenols do not cause a change of 14 elements in the whole blood of normal diet rats, but a variety of whole blood elements are changed when tea polyphenols are add on food restriction group rats which means people in dieting should be careful to add.5. The increase of Se content in the blood of high fat diet rats induced by tea polyphenols intervention might underlay the antioxidant activity of tea polyphenols and this increase effect is independent on the excretion of Se through urine.6. Tea polyphenols can increase the Zn content of whole blood of food restriction rats, which is independent on the excretion of Zn through urine;7. Effect of tea polyphenols on the increase of whole blood zinc levels of food restriction rats might underlay the interaction between tea polyphenols with zinc and the MT1 m RNA expression.8. Tea polyphenols have different effects on lipid metabolism and elements in rats under three dietary forms, suggesting that it is possible to take advantage of this phenomenon of tea polyphenols to promote better health. |
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